1. Field of the Invention
The present invention relates to a method and an apparatus for precisely cutting a flat type non-metal substrate, such as glass or silicon, into a plurality of pieces. More particularly, the present invention relates to a method and an apparatus for cutting a non-metal substrate, wherein a cutting laser beam which follows a scribing laser beam for cutting the non-metal substrate made of a non-metal material, such as glass or silicon is generated in a cutting route so that the non-metal substrate is precisely cut along the predetermined cutting route.
2. Description of the Related Art
Recently, as a semiconductor thin film manufacturing technique is developed, a semiconductor industry has technologically advanced in manufacturing high integration and high performance semiconductor articles. In the semiconductor article, tens of thousands semiconductor devices are integrated on one substrate of high purity by thin film manufacturing processes. The substrate referred to a wafer is made of single crystalline silicon, which is one of non-metal material. The semiconductor article stores data in the form of digital signals and arithmetically treats the stored data in a minute.
In addition, as an application of the semiconductor industry, a liquid crystal display (LCD) technique, which displays an image by converting an analog signal processed in a data processing unit to a digital signal, is rapidly progressed. In the liquid crystal display device, liquid crystal molecules are filled between two transparent substrates. The liquid crystal display device changes the alignment of liquid crystal molecules by applying an electric field to the liquid crystal molecules. By changing the alignment of liquid crystal molecules, optical properties of liquid crystal cells such as birefringence, circumpolarization, dichroism, light scattering, and so on, change to display various images.
The semiconductor device and the liquid crystal display device are commonly formed on a non-metal substrate, such as a silicon substrate of high purity or a glass substrate. Though the non-metal substrate is weak against the external impact, the non-metal substrate has the advantage that a plurality of semiconductor chips or a plurality of cell units formed on the wafer or on the glass substrate can be easily sliced into an individual semiconductor chip or a cell unit.
In case of the semiconductor device, hundreds of semiconductor chips are simultaneously formed on one wafer. Then, semiconductor chips are individually cut by a cutting process. After that, a packaging process is carried out with respect to the semiconductor chip thereby forming the semiconductor article.
In case of the liquid crystal display device, at least two LCD cell units are simultaneously formed on the glass substrate called as a motherboard. Then, after cutting the LCD cell unit from the motherboard by the cutting process, the cell unit is assembled with PCBs and so on.
At this time, since the cutting process is the almost final step in the manufacturing processes, the cutting fault reduces the productivity of the articles. Particularly, the motherboard used in the liquid crystal display device is made of glass and has no crystal structure. Accordingly, the motherboard is weaker than the silicon wafer. For this reason, a fine crack formed at an edge portion of the motherboard during the cutting process amplifies stress along the fine crack. This may cut undesired portions of the motherboard when executing the cutting process.
Conventionally, a diamond blade with fine diamonds fixed at a circumferential portion of a disc rotates at a high speed, on the cutting route to form a scribe line of a predetermined depth on a substrate. Then, the substrate is cracked along the scribe line by an external impact, thereby cutting the semiconductor chip or LCD cell unit from the wafer or the glass motherboard.
When cutting the substrate by using the diamond blade, a predetermined cutting margin is prepared on the wafer or the glass motherboard, limiting the number of semiconductor chips formed on the wafer if the cutting process is not precisely performed.
In case of the liquid crystal display device, a cutting plane cut by the diamond blade is roughly processed so that the stress is concentrated on the cutting plane. Accordingly, the external impact applied to the cutting plane generates crack and chipping portions in the cutting plane.
In addition, the diamond blade that generates a lot of glass particles requires separate cleaning and drying processes to remove the glass particles.
In order to solve the above problems, various cutting methods and apparatuses using a laser beam have been developed. For example, U.S. Pat. No. 4,467,168 discloses a cutting method by using a laser and a method for manufacturing articles by using the same. In addition, U.S. Pat. No. 4,682,003 discloses a method for cutting glass by using a laser beam and U.S. Pat. No. 5,622,540 discloses a method for cutting a glass substrate.
FIG. 1 shows a conventional apparatus for cutting a glass substrate by using a laser beam.
Referring to FIG. 1, a laser beam 1 is irradiated along a cutting route 3 of a glass motherboard 2 so as to rapidly heat the cutting route 3. Then, a cooling fluid beam 4 having the temperature extremely lower than the temperature of the heated glass motherboard 2 is radiated along the cutting route 3 such that the glass motherboard 2 is cut along the cutting route 3 by means of the tensile force caused by the rapid expansion and shrink of the glass motherboard 2.
The cutting apparatus shown in FIG. 1 can cut a relatively thin glass motherboard at once. Recently, the liquid crystal display device is required to have a large size so that the surface area and the thickness of the glass motherboard become increased. Especially, the present glass motherboard has the thickness over 0.5 mm. Accordingly, in order to cut the glass motherboard having the thickness over 0.5 mm at once, the laser beam 1 is required to have the extremely high energy level.
When the energy level of the laser beam I irradiated onto the glass motherboard 2 increases, the temperature difference between the cutting route 3 of the glass motherboard 2 and a periphery portion of the cutting route 3 is greatly increased. This temperature difference creates cracks, before the cooling fluid beam 4 cools the cutting route 2 at portions of the glass motherboard 2 where the temperature difference is greatly increased, cutting undesired portions of the glass motherboard.
In order to solve the above problem, an apparatus for cutting a glass substrate without using the laser beam having the high energy level is developed. The cutting apparatus is shown in FIG. 2.
In FIG. 2, a scribing laser beam 13 is irradiated along a cutting route 12 of a glass motherboard 10 so as to rapidly heat the cutting route 12. Then, a cooling fluid beam 14 having the temperature extremely lower than the temperature of the heated glass motherboard 10 is applied along the cutting route 12. Then, the glass motherboard 10 is rapidly cooled so that a crack having a predetermined depth is formed on the surface of the glass motherboard 10, thereby forming a scribe line 15. After that, both sides of the glass motherboard 10 are rapidly heated about the scribe line 15. Accordingly, both sides of the glass motherboard 10 are rapidly expanded so that a great tensile force is generated at the scribe line 15. As a result, the glass motherboard 10 is completely cut along the scribe line 15.
According to the cutting apparatus as shown in FIG. 2, the scribe line 15 can be formed even when the temperature difference between the heated cutting route 12 and the cooled cutting route 12 is not widely formed. In addition, since a shear stress is increased as the temperature difference between the scribe line 15 and a periphery portion of the scribe line 15 is increased, the cutting apparatus can cut a relatively thick glass motherboard at once.
However, since the cutting apparatus shown in FIG. 2 cuts the glass motherboard by using at least two beam patterns after radiating the cooling fluid beam, there is required to adjust the quantity and intensity of the beam patterns. In addition, the beam patterns have to be symmetrically adjusted so as to linearly cut the glass motherboard. Much time is necessary for symmetrically adjusting the beam patterns. Furthermore, since the laser beam has to form at least two beam patterns, a separate device such as beam splitter is required, complicating the optical system.
Therefore, it is a first object of the present invention to provide a method for cutting a non-metal substrate made of glass or silicon with a simple structure of an optical system.
It is a second object of the present invention to provide an apparatus for suitably performing the cutting method.
To achieve the first object of the present invention, there is provided a method for cutting a non-metal substrate comprising the steps as follows.
A first area of a cutting route is rapidly heated by irradiating a first laser beam onto a cutting route which is predetermined on the non-metal substrate. A scribe line having a predetermined depth is formed by applying a cooling fluid beam onto the heated cutting route. Then, the scribe line is rapidly heated by irradiating a second beam along a radiating route of a first laser beam thereby completely cutting the non-metal substrate.
To achieve the second object of the present invention, there is provided an apparatus for cutting a non-metal substrate comprising a first means for generating a first laser beam onto a cutting route formed in the non-metal substrate for heating the cutting route such that a scribe line is formed on the cutting route and for generating a second laser beam, which is spaced by a predetermined distance from the first laser beam, to form a beam pattern along a radiating route of the first laser beam. A second means forms a crack by applying a cooling fluid beam onto the cutting route formed between the first laser beam and the second laser beam.
To achieve the second object of the present invention, according to another embodiment of the present invention, there is provided an apparatus for cutting a non-metal substrate comprising a first means for generating a first laser beam onto a cutting route formed in the non-metal substrate for heating the cutting route such that a scribe line is formed on the cutting route and for generating a second laser beam onto the scribe line while maintaining a predetermined distance from the first laser beam. A second means forms a crack by applying a cooling fluid beam into the cutting route formed between the first laser beam and the second laser beam.
According to the present invention, the non-metal substrate is cut by using one beam pattern after applying the cooling fluid beam, so an optical system is simplified. In addition, the time for adjusting the beam pattern and the beam intensity is reduced.